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Standby vs Prime Power Generators

Updated: Oct 7, 2020

Read or listen to our Podcast - In this episode, we are going to discuss the differences between emergency standby, prime and continuous power rated generators.


Standby Power Rated Generators are the most commonly rated generator. They act as an emergency backup for when a regular source of power has failed. Home and businesses all use them. Hospitals, Emergency Services, and gas stations are just some of the places you can find emergency standby generators sitting ready to operate the moment a power outage occurs.

A quality emergency standby generator should also be capable of operating for days and weeks if needed. It can even provide power full-time, but emission regulations only permit them to be used for emergencies.

An emergency standby generator should have an average load, not exceeding 75% of the generator rated power. The additional 25% is there to help with motors, pumps, fridges, and freezers, for example, that all need extra power to start-up. Once started, they consume less energy to keep running. That reserve power is an important consideration.

Think of the power your car has and how you use it. There is enough power to accelerate hard and pass someone, but it will not last long, driving with the peddle floored full-time. It is not designed to work like that; neither is a standby generator.

Selecting the right size standby generator is essential. You want it to operate with loads falling between 40% and not exceeding an average load of 75%. You can surge up to 100% as part of its regular operation.

With a standby rated power generator, you can even exceed the rated power by 10% but not for long.


Prime Power Rated Generators should also operate at a 75% variable load, just like a standby generator. But, Prime power generators can be your only source of power.

Typical applications are for use as remote power at a job-site, off-grid home, RV, food or service truck, and any other place where there is no regular power available.

Some manufactures rate the same size generator a little lower when used for full-time prime power. It is to help extend the life of the engine. It should also be built to withstand non-stop operation but, so should any other generator.

There are also Continuous Power rated generators. They can run for an unlimited number of hours per year at 100% load, full time. You can't exceed the 100% continuous power rating at all. Overload of any kind is not acceptable, unlike Standby and Prime power generators. There is one other factor to consider, and that is emission regulations.

Emission regulations differ for different applications and regions.

Typically an engine approved for emergency standby use does not need to be as clean as one used for full-time power. Your generator dealer understands the differences and should never sell you something that does not follow current regulations. Just be sure to tell them what you are using the generator for!

In another podcast, we will discuss emissions further.

Thanks for listening. If you want to learn more about generators or are shopping for one, please visit us at AURORA GENERATORS .com or call us at 1-877-510-6807

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